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    <title>Document</title>
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    <script>
      //Q1 :在基本类型Symbol上，let和var声明的结果不同
      var s3 = Symbol('zhangshan');
      var s34 = Symbol('zhangshan');
      console.log(s3 === s34);
      let s2 = Symbol('hahah');
      let s2_2 = Symbol('hahah');
      console.log(s2 === s2_2);
      //Q2 : 如果不想用const常量块级作用域，怎么处理
      let cat = { age: 18, sex: 'nv' };
      cat = null;
      console.log(cat);
    //   const haha = 345;
    //   haha = 456;
    //   console.log(haha); //不能修改初始值
    
    </script>
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